Effect of Cu Addition on the Thermoelectric Properties of n-type and p-type β-FeSi₂

Abstract

The thermoelectric properties of n-type FelyCoySi₂Cux(0.02≤y≤0.06)(0≤X≤0.06) and ptype Fe_0.92Mn_0.08Si_2-xCux(0≤X≤0.07) were investigated. Mixture of Fe, Si and Co or Mn powders with or without Cu was arc-melted in an argon atmosphere to form a button composed of α -Fe₂Si₅ and ε-FeSi phases. The button was ground under -60mesh and Cu powder was mixed for the samples without Cu doping. Then they were ground (MA) in a conventional ball mill for 360 ks or in a high energy vibrational mill for 72 ks. β-FeSi₂ phase was not formed during MA, but was obtained by hot pressing of MA powders at 1173 K for 1.8 ks under 25MPa. It was found that the small addition of Cu improves the power factor(Q2/ρ) of n-type Fe₁-_yCo_ySi₂ by decreasing the electrical resistivity and increasing the thermoelectric power. On the other hand, for p-type Fe_0.92Mn_0.08Si₂ the electrical resistivity slightly increased and thermoelectric power decreased, as the result the power factor decreased. Cu addition slightly increased the thermal conductivity for both of n-type and p-type β-FeSi₂.